Colloidal sulphur and process of producing the same



Patented July 7, 1936 EJNHTED STATES PATENT OFFICE COLLOIDAL SULPHUR ANDPROCESS OF PRODUCING THE SAllIE No Drawing. Application August 28, 1933,Serial No. 687,171

15 Claims.

This invention relates to colloidal sulphur and to a process ofproducing the same.

Colloidal sulphur is a variety of sulphur that in consequence of thespecial treatment it has received readily dissolves in water to form acolloidal solution. Since the term colloidal is frequently loosely used,it becomes necessary to define the term colloidal sulphur as it is usedin this application. By the term colloidal sulphur in this application,I refer to sulphur consisting of such finely divided particles that whensuch sulphur is dispersed in water it forms a highly dispersed colloidalsolution, clear by transmitted light and slightly fluorescent byreflected light. In this sense-colloidal sulphur consists'of particleswhich are generally invisible in the ultramicroscope, although as asolution of the colloidal sulphur ages some particles become visibleultramicroscopically. I thus distinguish colloidal sulphur proper fromother so-called colloidal sulphurs, which, in fact, are not trulycolloidal but in which the particles are more coarsely dispersed,forming opaque solutions.

The activity of sulphur depends largely on its state of sub-division.For example, ordinary sulphur is fairly inert and may be introduced intothe human body in large quantities without producing any marked effects.Precipitated sulphur, which is in a finer state of sub-division than theordinary variety, is more active and hence this material findsapplication as an ingredient of sulphur ointments. Colloidal sulphursolutions, as herein defined, are very active and have been found topossess important curative powers. For example, ordinary sulphur isfairly inert and may be introduced into the body in large quantitieswithout producing any marked effects. Precipitated sulphur, which is ina finer state of subdivision than the ordinary variety, is more activeand this activity is taken advantage of in preparing sulphur ointments;milky suspensions of sulphur, in which the sulphur is still more finelydivided, are yet more active and have been found to possess remarkablecurative powers; finally colloidal sulphur solutions possess the verymaximum of activity, upon which fact depend the many useful applicationsof these colloidal sulphurs.

Heretofore, if colloidal sulphur has been produced it has been producedonly in such small quantities as to be merely a scientific curiosity orto furnish material for the study of the action of colloids.

It is the general object of the present invention to provide a processof producing colloidal sulphur which will permit the production ofcolloidal sulphur solutions in large and useful quantities.

It is a further object of the present inven- 5 tion to provide a numberof new products, including a new form of colloidal sulphur itself.

The present invention, together with various objects and advantagesthereof, will best be understood from a description of a preferred form10 or example of a process and product embodying the invention. For thispurpose, I have hereinafter described a preferred product and apreferred process of producing the same.

In the preferred process the colloidal sulphur 15 itself is produced bya reaction between concentrated sulphuric acid and sodium thiosulphate.

It is understood, of course, that other equivalent alkalinethiosulphates, such as potassium thiosulphate, might be substituted inthe process. 20 The reaction taking place between these ingredientsproceeds withthe formation of sodium sulphate, sulphur dioxide and waterin accordance with the following equation:

The sulphur produced from this reaction is the sulphur which is in thecolloidal state. In order that a material portion of the sulphur bederived in the colloidal state, it is important that 30 the reaction becarefully controlled and regulated. In the preferred process, I preferto' start with a bulky supply of concentrated sulphuric acid and add thesodium thiosulphate solution thereto slowly under carefully regulatedcondi- 35 tions of temperature and rate of addition of thiosulphatesolution. It is to be noted that it is essential to the production ofcolloidal sulphur that the thiosulphate solution be added to the bulksupply of concentrated sulphuric acid, as 40 the addition ofconcentrated sulphuric acid to a bulk supply of sodium thiosulphatesolution does not produce colloidal sulphur but merely precipitatedsulphur. The sodium thiosulphate solution most desirable is at aconcentration of 45 about 745 grams of thiosulphate per liter ofsolution. About 1200 m. l. of the foregoing sodium thiosulphate solutionare employed to about 500 m. l. of concentrated commercial sulphuricacid.

In the preferred process, the bulk supply of 50 the sulphuric acidsolution is first placed in a vessel and surrounded by suitable meansfor controlling the temperature thereof. In certain cases, it may besufficient to merely surround the container at the start of the processby ice. 55

Provision should be made forthe removal of the sulphur dioxide gas,which is generated continuously in the process, and also provisionshould,

be made for thoroughly agitating the thiosulphate solution during theprocess. For this purpose, any suitable agitating means, such'.as "amechanical stirrer, may be employed. The sodium thiosulphate solution isadded slowly, for example, at the rate of two drops a second :at thestart of the reaction to the concentrated sulphuric acid While the sameis stirred. In order.

to secure a maximum yield of sulphur in the colloidal state, acarefulwatch should be kept over the temperature which'rises' rapidly.at the start of the reaction. When the temperature reaches 40 C., therate of introduction of the'thiosulphate solution is best regulated, sothat the reacting mixture is maintained between-40 and 50 C., although afew degrees above or below the limiting temperature momentarily is of noconsequence.v .At other temperature ranges, if

gmaintainedz,during the process, the. percentage of sulphur produced inthecolloidal'formis much lower or its quality is impaired. A hightemperature produces high qualitysulphur but in small quantity; .A' lowtemperature produces a lower quality of sulphur but a larger quantity.

After about ten to twenty minutes the temperature of the reactingmixture begins to drop, at

which point the thiosulphate solutionmay be permitted to fiow morerapidly,-but it should not flow'faster than the smallest possiblecontinuous stream; Therate'of addition of the thiosulphate solutionshould be so regulated that nofoam forms sufficient to cover over thereacting. mixture and prevent the thiosulphate solution from makingimmediate contact 'with it. During the later stages of the process itwill be found necessary in order to keepthe temperature from falling tore move the ice and water surrounding the container of thereactingmixture, and finally to provide heat to the. reacting mixture, forexample, by supplying hot water to the spacesurrounding the container ofthe reacting mixture. As soon as the addition of thethiosulphatesolution has been completed, the reacting mixture is broughtrapidly to 50- C. and stirred vigorouslyuntil the foam hasdisappeared'fromits surface. 'It'is then diluted by the addition, forexample, of about 1400 mllpof distilled Water'at 50 C.

At the completion of the reaction, without permitting the contents todrop: below a temperature of substantially 45 C., the reacting mixtureis filtered, for example, through cheese cloth, in order to remove thatportion of the sulphur which is -in.an undissolved andnon-colloidalstate. It is :important that this filtration be carried outat a temperature high enough to keep the soluble :or

colloidal sulphur from coagulating and clogging the filter.

By this process there is produced a solution-oi? sodium sulphate withexcess sulphuric acid present, possibly undecomposed sodiumthiosulphate, various :polythionic acids, and sulphur dioxide.

' .massbecomes mushy and viscous, and;.if temiuble sulphur thatgradually precipitates out.

peratures above 10 C. are permitted the sulphur will not be completelyprecipitated from the solution. This refrigeration and settlingoperation causes the colloidal sulphur in the solution to separate outand it is then filtered from the liquor. The acoagulated sulphur thusseparated is then redissolved by hot water, which preferably should bedistilled water or soft water free from calcium,

magnesium, and iron compounds, as the presence of these compoundsisdetrimental to the maintenanoe'of the colloidal condition of thesulphur. For example, enough hot water is then added to the coagulate'dsulphur to bring the contents to a volume of about 750 m. 1. By means ofstirring -andlheating on a water bath to, for example, 50

C., the coagulated sulphur is all dissolved, with the exception of asmall amount of very fine insol- If it is noticed that the insolublesulphur thus precipitated out is large in amount, it is preferable Iito'refrigerate the solution to further settle out the insolublesulphur.

'After rthese operations, the colloidal or dis- .solved sulphuris nowready for purification. The

' purification operations preferably are conducted by;.alternatelycoagulating the same with saturate'dsaltgsolution'tofree'the sulphurfrom the impurities-units motherliquor, decanting the mother liquor,redissolving the solidsulphur, and repeating thesep'perations until allundesirable impuritieshavebeenremoved important feature in theproduction of substantial-amounts'of colloidal sulphurin the puri- -fiedstat-efis a proper control of the temperature *during these successivecoagulations of the colloidal sulphur. For example, in the preferredprocess ofpurifying the colloidal sulphur the sul- "phursolutionjisbrought toa temperature of about 50 C., an'd therelis added about 300 m.l. of a sat- 'urated salt solution, which is likewise preferably atatemperature of 50 C. The result of the ad- "dition of the saturated:salt solution is to coagulate and precipitate the colloidal sulphur.The admixture is preferably permitted to stand in arefrigeratorforraboutfifteen hours, at which time the coagulated sulphurwill havesettled into 'a :solid mass.

The liquorlis then pouredoff the coagulated :solid sulphur and the solidmass drained free of .theiliquid. The-solid block of colloidal sulphurthus derived-is then dissolved in warm distilled water and brought to avolume of about 500m. 1. -It:is again brought'to 50C.;anda further'quan- 'tity pf salt solution at 50 Cpadded thereto, for

example, 15.0 :m. lxof salt solution is added, the mixture stirred andthe sulphur again coagulated and precipitatedlin amass, as before. Theoperations or permitting the mass to set again for fifteen :hoursrandseparating the solid sulphur derivedzfrom the liquor arelrepeated. Thesesteps of: alternately dissolving the solid sulphur in water andcoagulatingthe sulphur 'with saturated salt solution arerepeated'oneormore additional times, at the-endotwhichtime the solid sulphur resultingfrom one of the coagulating operations is re- :dissolvedin water atabout 50 C. and then the solution permitted to settle in a refrigeratorto in"thismannercompletely coagulate the sulphur. The sulphurzisseparated from the remaining liquor and again dissolved in-water'toobtain about :a 5.0% sulphur solution. This sulphur solution at theendof-these operationscontains about 10% common :salt remaining from theconcentrated salt solution used in the operations of coagulating thesulphur "and separating :it, from the products of the original reaction.The sulphur'fsolution thus obtained may be diluted to any desired extentwith distilled water. A 10% solution of sulphur is the one which isfound most useful in practice. To this sulphur solution there may beadded a small amount of concentrated hydrochloric acid in order toimprove the keeping properties thereof. For example, about two tenths of1% of concentrated hydrochloric acid is added to the 50% sulphursolution before dilution.

It is also possible to remove some of the sodium chloride or electrolyteby dialysis, although it I is not recommended that this be done for mostpurposes. To effect this, the concentrated sulphur solution may beplaced in a parchment bag and dialysed against running distilled waterfor about three days. At'the end-the sulphur solution will be found tocontain about 29% sulphur and about 1.9 of sodium salts. .7

I have also discovered that the colloidal su1-' phur solutions may bemixed with alcohol in various proportions. For many purposes, thisalcoholic solution has an advantage over. the purely aqueous solution.The alcoholic: solutions are rendered more stable if a slight amount .ofhydrochloric acid is added, as in the case with the water solution.These alcoholic solutions also contain sodium chloride resulting fromthe coagulation operations. For example, I have produced most desirablesolutions which include from 15% to 30% of alcohol, by volume; and about5% to 10% colloidal sulphur.

In order to prepare stronger alcoholic solutions of colloidal sulphur, Idiscovered that the colloidal sulphur must be entirely freed from sodiumchloride and this latter salt replaced by an acid. Although tartaric,citric, and other acids may be used for this purpose to: some extent, Ihave found that concentrated hydrochloric. acid is the only one that isentirely satisfactory. Sulphuric acid can not be used. 1

The process is as follows: To a very strong (50% or more) ordinaryaqueous solution of colloidal sulphur with the usual amount of sodiumchloride in it, is added a large excess of concentrated hydrochloricacid, the whole being surrounded by a freezing mixture of ice and salt.The sulphur is precipitated in a rubbery mass that after standing for 18hours is compact enough to permit decantation of the supernatant liquid.

The coagulum of colloidal sulphur is well pressed to extract all themother liquid possible, after which it is dissolved in a minimumquantity of water, and the whole operation of adding the hydrochloricacid, refrigeration, and so on, repeated. Another repetition of thisoperation completely replaces the salt with hydrochloric acid. The thirdresidue will dissolve in either Water or alcohol and remains as stableas a chemically pure colloidal sulphur solution does.

With this sulphur-hydrochloric-acid sol., stable solutions containing70% absolute alcohol by weight and up to 20% of colloidal sulphur may beprepared. The most useful of these alcoholic solutions I find to bethose containing from 5% to 20% colloidal sulphur and from 30% to 60%absolute alcohol by weight.

While the particular form of product and process herein described arewell adapted to carry out the objects of the present invention, variousmodifications and changes may be made without departing from theprinciples of the invention, and this invention includes all suchmodifications and changes as come within the scope of the appendedclaims.

I claim: e

1. A process of producing a. colloidal sulphur, which comprises adding athiosulphate solution to a bulk supply of sulphuric acid so as to formsulphur in the colloidal condition, while maintaining the reactiontemperature mainly between 40 and 50 C.

2. A process of producing a colloidal sulphur dispersion,-which-comprises adding a thiosulphate solution for a bulk supply ofconcentrated sulphuricacid' to form sulphur in the colloidal state; andthereafter'purifyin'g the colloidal sulphur by coagulation of samethrough" the addition of a substantially saturated'sodium chloridesolution, cooling,"and s'ettlingiand separating the coagulatedsulphur'from the mother liquor, and

redispersing the coagulated sulphur.

tween and 50 C., and purifying the'colloidal sulphur dispersion bycoagulation of the colloidal sulphur by the. addition of a concentratedsalt solution, cooling, settling and separating the coagulated sulphurfrom the 'mother liquor, followed by dispersion of-the coagulatedsulphur.

5. A process of .producing acolloidal sulphurdispersion,.-:.,which:comprises slowly adding to a bulk supply ofconcentrated sulphuric acid a thiosulphate solutionto form-sulphurin thecolloidal state, and separating the colloidal sulphur from the reactingmaterials by coagulating the same with a substantially saturatedsolution of sodium chloride cooling, settling and separating thecoagulated sulphur from the mother liquor, redispersing the coagulatedsulphur, and subjecting the redispersed sulphur to one or moreadditional coagulations with saturated sodium chloride solutions.

6. A process of purifying a colloidal sulphur, which comprises adding asubstantially saturated solution of sodium chloride to the colloidalsulphur dispersion at a temperature of about 50 C. and then cooling theadmixed solution to a temperature of about 0 C. suitable for coagulatingthe sulphur, separating the solvent from the coagulated sulphur andredispersing the coagulated sulphur in water.

'7. A process of purifying a colloidal sulphur, which comprisesdispersing colloidal sulphur in water and heating to about 50 C., thenadding a substantially saturated solution of sodium chloride to thecolloidal sulphur dispersion, said solution of sodium chloride beinglikewise heated to about 50 C., and then cooling the admixed solution toa temperature of about 0 C. suitable for coagulating the sulphur,separating the solvent from the coagulated sulphur and redispersing thecoagulated sulphur in water at a temperature of approximately 50 C.

8. A process of purifying a colloidal sulphur, which comprises bringinga dispersion of the colloidal sulphur to a temperature of about 50 C.,

dium chloride, :and containing av'small .percening at:approxima.te ly=50c 'cthenacooling the 'arimixed dispersionlandgsolution'toeaflowtemperature for tseverallhour's; removingithe liquid .iirom thecoagulate, iandz-redispersing the;solid:sulphur mass in distilled water:or iordinary 2potable zwarter :free -iIr,om-'salts=:ofrcalcimnhmagnesium, iron 7 and-aluminum. v

.10.;A .process of pm'itymg the icolloidal sul- :phur which is:dispersed :in zaqueous:i-veliicle,v

which comprises adding .to "such rcolloidal sulphur dispersion asubstantially-saturatedsolution :of sodium chloride, :both dispersionand solution being :at :approximately ;50 0,, then cooling 1 the admixeddispersion :and solution 'to a low temperature 101' several ,hours,:removing :the liquid from .thercoagulate,i'redispersmg the solidsulphur ;mass in distilled "water 'byaheating on a waterlbath.tocsubstantially fimac. and chilling for several ;hours";or-.-m1til thesulphur icoagulates in a solid mass, repeating eration a :second '1time;

;11. As a new product, rcolloidal :sulphur :dispersed in a "solventcomprising. alcohol and water and :containing 728' :substantial amountor rsovtage of :hydrochloric acid.

12. ..As .a :new product, 2 0011011181 :sulphurx-disthevop- V:agulantmllowing the dispersionxto cool to a temidrochloric acid, :butwith no sodium chloride ipresent. V

113. A' .process of producing highly dispersable .colloidalr'sulphur,which comprises adding a thio- "sulphate solution :toa .bulk supply ofsulphuric :-acid;in-za,fine stream while vigorously agitating thesolution and -maintaining the temperature 1between:40-and 50 cthereafter filtering off the -vundispersed sulphur, allowingithe. liquidcontain- .ingdche :colioidal sulphur to cool to allow tem- V Vperaturernear0 C. for a :number -.of' hours, and :separating thecoagulated colloidal sulphur from the 1110171181? liquor.

14. A process, :asiin ;claiml 13, wherein the :comatedsulphurisdispersedin water at a. temperature of about 550 0,, .;and a substantiallysaturated ."SOllllJi'OIl :or sodium chloride likewise at atemperature:ot150 1C. added thereto, the

nnixedssolution "anddispersion then being ,cooled to near 0 -"C. to.re-coagulate .the :sulphur, and

decanting therisupematant liquorand redispersiingzthezcoagulated sulphurin water.

15.; A2procesS-bf purifying colloidal sulphur dis- :persion :produced:from the reaction of thiosuliphate "on sulphuric ;;acid, whichcomprises first subjecting the colloidal sulphur to one or morecoagulations'bytheiaddition of salt and cooling ?followed byredispersion of the sulphur, and

thereafter dispersing the colloidal sulphur in a aminimum quantity forwater at a temperature 'ofab:out 50 fC.,-Jandfthen without'addition ofc0- ,peratureiof near 0 C..,-and removing the supernatantliquid;repeating :the operation at least *onezadditional timeusingsubstantially the mini- ;mum amount ofwater to'dissolve thecoagulant :therebypurifyingsame 'from'the salt used as a 40 coagulant.

a IRVING :MILLER.

